Tecnologias aeróbias no tratamento de resíduos da produção animal: compostagem e vermicompostagem.

Abstract

This study aimed to evaluate composting and vermicomposting for treating residues of animal production. Two trials were conducted. The objective of the first trial was to evaluate rice hulls as structuring agent of composting, along with the proportion of residues of marine fish and rice hulls and the composting process. The composting system had two steps: composting cells and composting pile. The mixture proportions evaluated during 90 days of trial were: 3kg of rice hulls : 1kg of residues of marine fish (T1) and 3kg of rice hulls : 3kg of residues of marine fish (T2). Both had five replications. Biomass temperature showed that mesophilic population was present during the whole experimental period in both treatments. The linearity of the equation model and its high coefficient of determination (R2 = 0.98) showed that air environmental temperature influenced biomass temperature in T2, with a quadratic trend. The C/N ratio of T1 at 60 days of composting was significantly higher than T2 (P<0.05). The objectives of the second trial were: (1) to evaluate composting systems through active and passive aeration methods, along with vermicomposting of a mixture of bovine liquid residues and poultry bed; (2) to compare the association between passive and active aeration composting with passive aeration composting followed by vermicomposting; (3) to compare the compost and vermicompost obtained at the end of trial. For composting through passive aeration a 12m length, 2m width and 1.80m height structure covered with film of low density polyethylene was used. Such structure housed three 1000L plastic boxes reinforced with glass fiber. For composting through active aeration, a pile was formed containing part of the biomass from the mixture of bovine liquid residues and poultry bed. The 12 experimental unities for vermicomposting were the wooden boxes. A total of 200 adult Eisenia fetida (Savigny, 1826) earthworms were mixed with the substrates. The composting through passive aeration significantly reduced total organic matter, total organic carbon, pH and potassium levels. In contrast, ash, total phosphorus and total calcium were significantly increased (P<0.05) during the process. The composting through active aeration favored significant decreases of total organic matter, total organic carbon, carbon/nitrogen ratio and total potassium. Additionally, there was a significant increase of ash, total nitrogen and pH (P<0.05). Vermicomposting leaded to significant reductions of total organic matter, total organic carbon, carbon/nitrogen ratio, ash, total nitrogen, total phosphorus and total potassium (P<0.05). The combination of composting through passive aeration and vermicomposting leaded to a significant reduction of total organic carbon, carbon/nitrogen ratio and carbon/nitrogen ratio. Significant increase of pH, ash, nitrogen and calcium were observed. In conclusion, vermicompost was significant superior than composting as an organic fertilizer (P<0.05).